The invention relates to apparatus for cutting insulation or like sheet material, especially for lining ductwork, such as radius elbows and O.G. sets. At the present time, such insulation is conventionally cut by hand, a great deal of time and effort being necessary for an individual doing the cutting to set up the proper arcs that are to be cut, making sure that the right radius is cut, etc. Also, it is difficult to cut with a great deal of precision when making the arcuate cuts, so the end product may not have an exact fit on the ductwork to which it is to be connected. According to the present invention, these problems are avoided by providing a simple mechanical system for quickly setting up and changing the patterns to be cut, and positively guiding the arcs and radial cuts that are to be made.
While there are many prior art cutters that per se are adaptable for making two arcuate concentric cuts at the same time (see, for example, U.S. Pat. Nos. 1,841,099, 1,389,765, and 2,677,887), none of these prior cutters are adaptable for the quick set-ups and cuts that are necessary according to the present invention, nor do any of them provide cutting means that are particularly effective for cutting insulation, as is possible according to the present invention. According to the present invention, apparatus is provided that includes a pivot post, a first trammel tube, a second trammel tube telescopically movable with respect to the first trammel tube, means for mounting the first trammel tube for radial movement with respect to the pivot post, means for retaining the first trammel tube in one of a plurality of radial positions with respect to the pivot post, means for retaining the second trammel tube in one of a plurality of radial positions with respect to the first trammel tube, a first cutter wheel disposed on the bottom of the first trammel tube, and a second cutter wheel disposed on the bottom of the second trammel tube. The cutter wheels may be disposed in a first position in line with the tubes whereby radial cuts may be made therewith, or in a second position disposed 90.degree. with respect to the first position so that arcuate cuts may be made therewith with the pivot post generally at the center of the arcs being cut. With the trammel tubes in proper relative position, and the cutter wheels in arcuate cutting position, the apparatus is pivoted about the pivot post, and even, true cuts are made in the insulation with a minimum of skill required by the user of the apparatus.
It is the primary object of the present invention to provide apparatus that allows the quick and efficient cutting of insulation or like sheet material for lining specially ductwork and the like. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.